I mainly cover transport and infrastructure, along with workplace diversity. You can email me on Rebecca.smith@cityam.com with stories and commentary.

The government's decision has not been short of critics (Source: Getty)

Rebecca Smith

Mayor of London Sadiq Khan has stuck by his pledge to stand against Heathrow expansion, saying he will support a legal challenge to the government's decision.

He has directed Transport for London (TfL) to provide advice and assistance to affected borough councils, including Hillingdon, Richmond, Wandsworth and Windsor and Maidenhead as they prepare for a joint legal challenge with Greenpeace against a third runway at Heathrow.

It is expected that TfL will be named in this action as an interested party; as and when that is the case, the Mayor will take a decision on joining the legal challenge.

"I promised I wouldn't just stand by and see hundreds of thousands suffer from the additional noise and air pollution that a third runway would cause. These decisions show that I'm ready to help ensure that this misery isn't inflicted on Londoners," Khan said.

That’s why I’ve directed TfL to provide their expert advice and assistance to support Hillingdon, Richmond, Wandsworth and Windsor and Maidenhead Councils, and Greenpeace as they prepare for a joint legal challenge, and why I will be ready for us to play an active role in the action if required.

Leader of Wandsworth council Ravi Govindia said: "The mayor's commitment is very good news and will significantly strengthen our legal arguments. Transport for London's resources and technical expertise will be hugely helpful to developing our case and exposing the deeply flawed logic supporting Heathrow expansion."

As part of his mayoral direction, Khan directed TfL to further assess the impact on London of the proposed Heathrow expansion, and work closely with the government during the preparation of its national policy statement and planning process.

Last month, the government plumped for Heathrow after a number of delays on the airport expansion decision, with transport secretary Chris Grayling saying a new runway will "improve connectivity in the UK itself and crucially boost our connections with the rest of the world, supporting exports, trade and job opportunities".

A Heathrow spokesman told City A.M.: “The Airports Commission’s detailed work represents a solid foundation to support a Government decision for the third runway, and we are confident that any legal challenge would be unsuccessful and would not affect the timeline for delivering a third runway. We want to work with the mayor to ensure that Heathrow expansion helps London thrive as a global hub for talent, tourism and trade.”

The chief executive of London Chamber of Commerce and Industry has warned that any further delays to the airport process would just hinder, rather than help the capital.

Colin Stanbridge said: "Not everyone may have agreed with the government's decision last month, but we all need to get behind it now and recognise that expansion at Heathrow is the best chance we have to future proof our economy."